Improvement in pressure-gages



2Sheets -Sheetl' G. SEWELL. Pressure Gages.

Patented August 26, 1873.

INVENTOR WITNESSES 1 ZSheetv-Sheet 2. G. $E WELL. Pressure Gages.

N 142,128, PatentedAugust26J873.

r l illilf l l1 lllll)l|| WITNESSES INVENTOR Wu! e /ulmzl CI UNITEDSTATES PATENT OFFICE.

.GEORGE SEWELL, OF BROOKLYN, ASSIGNOR TO WILLIAM KING PHILLIPS,

OF NEW YORK, N.

IMPROVEMENT IN PRESSURE-GAGES.

Specification forming part of Letters Patent No. 142,128, dated August26, 1873; application filed December 17, 1872.

To altwho'ln it may concern:

Be 1t known that I, GEORGE SEwELL, of the c1ty oi Brooklyn, and countyof Kings,

- in the State of New York, have invented certain new and usefulImprovements in Steam- Gages; and I do hereby declare the follow-- ingto be a full and exact description of the same, the construction ofwhich is fully shown in the accompanying drawings making a part of thisspecification, in which- Figure 1 is a front view. Fig. 2. is a trans-.verse section of the same; Fig. 3, an enlarged view of I the glass tubeand its inclosing-case; Fig. 4, an enlarged view of small piston f and 4a portion of its cylinder and packing d and d.

tube 8, and also as a support for the dial a:

and its appurtenances. B Bis the casting, which is accurately bored forthe reception of the differential pistons f and g. 0.0 is the casting,in which is located the valve 1) and its seat, and serves to contain themedium 0, through which the steam acts on the piston f. The space 0above amalgam c is intended as an air-chamber, the object of which is toallow amalgam c to expand in obedience to ohan ge of temperature of thesurrounding air withoutraising small piston f, by which the zeropoint ofthe gage would be altered. For this material I make use of a metallicamalgam of mercury, lead, tin, or both, or any other suitable metal thatmercury will take up and still maintain the requisite fluid state, theproportion being regulated by the quantity of each metal that will betaken up by the mercury, and at the same time remain sufficiently fluidfor the purpose intended.

The amalgam consists of mercury and as much tobacco-wrapping foil(composed of tin and lead) as the former would take up. The object ofthis amalgam is to protect the pack ing or piston f from rapiddeterioration by immediate contact with the steam.

Air can be employed in place of amalgam c for the purpose of protectingpacking d from immediate contact with steam by intervening a body ofmercury between chamber containing amalgam c and floating valve 1).

. I employ amalgam c instead of mercury for the following reasons First,it will reduce the cost of the manufacture of the gage. Second, it willhave less aftinity for the sulphur in the rubber packing d. Third, itsgrade of expansion will be reduced, hence less liability to disturb fromits normal position small piston f.

To prevent the loss of this medium in the handling of the gage, eitherby accident or design, I employ the valve 12, which will always be keptclosed by the pressure of the amalgam, but will open in obedience to thepressure. of the steam, and allow it to act in forcing up small pistonf, and will close when the pressure is removed, and so keep the fluidfrom escaping. The lower end of the small piston f is covered by acup-shaped packing, d, and the upper piston g by a similar packing, 0,made of India rubber, non-porous animal membrane, or other suitablematerial, which are so arranged relatively to the movements of thepistons in obedience to pressure, as shown in the accompanying drawings,that when the pistons f and g are raised by pressure under piston f thepacking will become relaxed instead of stretching, as is the custom insome other gages, thus leaving the true indications of the gageunopposed by any extraneous opposition; hence the pressure indicated bythe index m will exactly conform to that due to the weight of themercury column. To any convenient part of the pistons f and g, or theconnection between them, I attach arm'i to secure rod j, through whichmedium index 112 receives its motion as the pistons rise or fall.

The chamber above the large piston g is filled with mercury h, which isforced up the glass tubes as the piston rises; This tube is inclosed andprotected by the metallic casing of the instrument u, and is kept inplace by plaster of Paris or other suitable cement.

At the upper end of the case 1: and the tube 8 a chamber, 0, is formedfor the purpose of receiving the mercury should the gage be inverted byaccident or design. This chamber 0 is closed with a tight-fitting plug,1), having air-passages 1" r 1' leading into the annular space y yformed between the outside of chamber 0 and protecting flange of plug1). mercury h will have continued communication with the atmosphere andshould the gage be inverted the mercury h would not fill chamber 0sufficiently to escape through th e air-passages a r r. The annularspace y y is for the purpose of concealing from view the externaltermination of air-passages r r r, and thus prevent tampering with byevil-disposed persons.

To insure the return of the mercury from chamber 0 upon the gage beingrighted, I place in the tube s a thread of woolen yarn or other similarmaterial, as shown at o o in the enlarged view, Fig. 3. This allows theair to pass up through it, while the mercury passes down on the outsideof the same to its proper position above piston 9, thus preventing thebreaking of the mercury column, which might occur through the opposingpressure of the confined air in chamber above piston g. The same resultmay be secured by placing a small tube (as a thermometer-tube) by theside of the tube 8, and allowing the upper end in chamber 0 to projectsome distance above tube 8 for the air to ascend while the mercurypasses down tube 8.

In order to have the least possible weight to oppose the steam-pressureother than the column of mercury, also to employ a material that willnot corrode, also as a means of reducing the cost of manufacture,Iconstruct the pistons f and g, and the connection between them, out ofvulcanite, or other suitable material, that is lighter than metal, bywhich means I am enabled to construct a differential piston steam-gagewith the zero-point nearer the true 0 than I otherwise could were I touse metal for the purpose.

I construct the valve 1) and its seat of vulcanite for the reason thatit is lighter than metal, and will not be liable to damage and to Thusthe leak from corrosion 5 also, as a means of cheapening the manufactureof the gage. Other portions of the gage could be made of vulcanite orother suitable material lighter thanmetal for the same reasons.

The quantity of mercury h is intended to consist of but a trifle moremercury than the capacity or bore of tube 8, which enables me toconstruct a mercurial gage in which the 0- point will be but littleaffected by changes of temperature, thus dispensing with an adjustableindex or scale, as in Browns gage, and the adjustable plug, as in A. S.Greens gage, and others, to adjust the 0 -point.

To prevent the possibility of undue friction on small piston f in theevent of the rubber packing or cap d becoming soft and adhesive from anycause whatever, I place a cap, of cloth or kid or any other suitablematerial, between therubber packing and small piston f, as shown at d inenlarged view, Fig. 4..

I do not claim, broadly, a differential piston steam-gage; but

What I claim as my invention, and desire to secure by Letters Patent,is-

.1. Mercury h, amalgam c, air-space c, and differential pistons f g, incombination with the arm '13 and rod j, substantially as hereindescribed, for the purpose of imparting motion to mechanism, whereby thepressure of steam may be indicated.

2. The floating valve b, arranged substantially as described, incombination with the chambers c, for the purpose set forth.

3. The chamber 0, with its plug 1; and passages r r r, constructed andarranged substantially as shown and described, to retain the mercury butallow communication with the atmosphere.

4. The strand of yarn or other fibrous material through the tube 8,substantially as and for the purpose herein described.

GEORGE SEWELL.

